A point is moving with position vector r

Python Inputs:

import numpy as np

from sympy import $*$

t $=$ symbols$(\text{'}$t$\text{'},$ real $=$ True$)$

r $=$ Matrix$([$t$**2-3,$ t$**2-$ t $+3,0])$

t$\_$v $=1$

What is the normal basis vector en at t $=1?$